USAID administrator Raj Shah, left, looks on as U.S. President Barack Obama, center, talks to Nimna Diayte, president of the Farmers Federation, front, during a food security expo on Friday, June 28, 2013, in Dakar, Senegal. Obama met with farmers, innovators, and entrepreneurs whose new methods and technologies are improving the lives of smallholder farmers throughout West Africa. (AP Photo/Evan Vucci)

DAKAR, Senegal (AP) — President Barack Obama is receiving the embrace you might expect for a long-lost son on his return to his father's home continent, even as he has yet to leave a lasting policy legacy for Africa on the scale of his two predecessors.

Presidents Bill Clinton and George W. Bush passed innovative Africa initiatives while in the White House and passionately continue their development work in the region in their presidential afterlife. Obama's efforts here have not been so ambitious, despite his personal ties to the continent.

His first major tour of Africa as president is coming just now, in his fifth year, while Bush and Clinton are frequent fliers to Africa. Bush even will be in Dar es Salaam, Tanzania, next week at the same time as Obama, although they have no plans to meet. Instead, their wives plan to appear together at a summit on empowering African women organized by the George W. Bush Institute, with the former president in attendance.

For Obama, one potentially memorable aspect of this trip -- a meeting with former South African president and anti-apartheid leader Nelson Mandela -- remained in doubt. Obama was en route from Dakar Senegal to Johannesburg, South Africa, Friday where Mandela was hospitalized in critical condition.

Obama, speaking to reporters aboard Air Force One, said it was uncertain whether he would get an opportunity to see the 94-year-old Mandela, a personal hero to the president.

"I don't need a photo-op, and the last thing I want to do is to be in any way obtrusive at a time when the family is concerned about Nelson Mandela's condition," he said.

In French-speaking Senegal, Africa's westernmost country, spirited crowds greeted Obama on his visit, with revelers frequently breaking into song and dance at the sight of the first African-American president. However thrilled they were to see him, many said they wish his visits weren't so rare.

"Two visits in five years, it's not enough," said Faye Mbissine, a 30-year-old nanny who took an early morning bus to come see Obama on Thursday outside the presidential palace. "We hope that he can come more."

Manougou Nbodj, a 21-year-old student, said he hopes Obama will bring American resources like jobs and health care. "If Obama can work with Macky Sall the way that George Bush worked with Africa before him, then we will be happy," he said, referring to the Senegalese president.

One of Bush's chief foreign policy successes was his aid to Africa, including AIDS relief credited with saving millions of lives and grants to reward developing countries for good governance. Bush followed on momentum on African policy that began under Clinton, who allowed several dozen sub-Saharan countries to export to the U.S. duty-free.

Obama has continued the Bush and Clinton programs during tough economic times. But his signature Africa policy thus far has been food security, through less prominent programs designed to address hunger with policy reforms and private investment in agriculture.

On Friday, Obama toured displays in small thatched booths at his hotel grounds on a bluff overlooking the ocean, meeting with farmers and entrepreneurs who are using new methods and technologies to advance the cause of food security.

"This is a moral imperative," he said. "I believe that Africa is rising and it wants to partner with us not to be dependent but to be self-sufficient.

Witney Schneidman, former deputy assistant secretary of state for African affairs, said Obama's efforts are not like Bush's AIDS initiative "where you put people on a medicine to save their lives — very, extremely important. This is more of a structural change, and I think that's going to take time."

Under Clinton and Bush "you had this major funding, major attention, major initiatives going to Africa, and then President Obama came in, and there was a sense of stall, in a way," said Jennifer Cooke, director of the Africa program at the Center for Strategic and International Studies. She said that's understandable as he grappled with wars and an economic crisis, and she gave Obama credit for working diplomatically with African governments in his first term.

But, she said, "they weren't big, splashy initiatives that got peoples' attention either in Africa or here at home, and no big money and no big ideas that really helped define what Obama was about in Africa."

That's a disappointed those who were expecting more from the first African-American president, especially after his speech during a brief stopover in Ghana his first summer in office, in which he spoke personally of his father's life in Kenya and declared "a new moment of great promise" in Africa. "I have the blood of Africa within me," Obama said.

Schneidman argued that Obama's personal connection may also have been an impediment to deeper engagement in his first term. "The whole birther movement here in the U.S. that was sort of questioning his place of birth to begin with ... I think it was a real constraint on dealing with Africa," Schneidman said.

Mwangi Kimenyi, a Kenyan who directs the Brookings Institutions' Africa Growth Initiative, said Obama may be a victim of misplaced sky-high expectations on the continent when he was first elected.

"Africans still consider Clinton their president," Kimenyi said. "If you go to Africa and mention Clinton — I mean, he is a hero, even today. I don't think President Obama is going to approach the level of President Clinton at all, in terms of respect, in terms of what they feel, and it's partly because, as one whose family is from Africa, the expectations were rather high."

"There is not that feeling that, you know, we have our son there," Kimenyi said. "There's probably more reference of a prodigal son than a, you know, son."

Clinton first drew extensive attention to Africa in 1998 when he made the longest trip ever by a U.S. president, with stops in six countries that had never before been visited by any occupant of the Oval Office.

Bush's trip this week is his third in 19 months to promote his Pink Ribbon Red Ribbon partnership to combat breast and cervical cancer in sub-Saharan Africa and Latin America. On this visit, he and his wife, Laura, plan to help renovate a cervical cancer screening and treatment clinic in Zambia before heading to Tanzania for the African First Ladies Summit advocating investment in programs for women and girls.

"Frankly, Africa is a place that we had not yet been able to devote significant presidential time and attention to," Obama foreign policy adviser Ben Rhodes said. "And there's nothing that can make an impact more in terms of our foreign policy and our economic and security interests than the president of the United States coming and demonstrating the importance of our commitment to this region."

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